Cutaneous T cell lymphoma (CTCLs) is the second most common extranodal non-Hodgkin's T cell lymphomas in adults. A recent WHO-EORTC consensus classification (Willemze R. et al. Blood 2005, 105:3768-3785) indicates that there are thirteen clinically and histologically distinct types of CTCL; however, 90% of CTCLs fall into three classes; mycosis fungoides (MF), primary cutaneous anaplastic large cell lymphoma (ALCL), and Sezary syndrome. The most common type of CTCL, mycosis fungoides, is characterized by erythematous patches and plaques that most commonly contain CD4+ T cells that show an affinity for the epidermis, or epidermotropism (Willemze R. et al. Blood 2005, 105:3768-3785). Staging is based upon a TNM classification; patients with Stage 1A disease have normal life expectancies, while patients with Stage 1B or greater have a diminished life expectancy (Kim, Y. H. et al. Arch Dermatol 2003, 139:857-866). Patients with Stage II-IV disease have a median survival of less than five years, with large cell transformation often leading to accelerated deterioration (Kim, Y. H. et al. Arch Dermatol 2003, 139:857-866). Sezary syndrome is a leukemic variant of CTCL wherein clonal CD4+ T cells accumulate in blood and lymph nodes as well as skin; five year survival is less than 25%. Primary cutaneous ALCL has a much less aggressive course, with a five year survival of 95%; however, cutaneous ALCL with concurrent nodal involvement is more aggressive (Willemze R. et al. Blood 2005, 105:3768-3785; Kadin M E, Carpenter C. Semin Hematol 2003, 40:244-256).
There is significant immune dysfunction in CTCL patients, with global dysregulation of the T cell repertoire of unknown etiology (Yamanaka K. et al. Clin Cancer Res 2005, 11:5748-5755; Yawalkar N. et al. Blood 2003, 102:4059-4066). The terminal event in most patients is bacterial sepsis. Current therapies for advanced MF and Sezary syndrome are palliative and durable long-term remissions are rare (Querfeld C. et al. Curr Opin Hematol 2005, 12:273-278). Thus, there is an urgent need for more effective therapies.
Current hypotheses indicate that aberrant T-cell activity is a likely driver in the pathophysiology of CTCL. Of particular importance is the observation that malignant T-cells may play a role akin to regulatory T cells and as such supress antitumor activity in CTCL. The CC chemokine receptor 4 (CCR4) is expressed at high levels on malignant, skin homing T-cells that are present in CTCL, as well as on regulatory T-cells (Tregs). Tumor cells secrete the chemokines CCL17 and CCL22 which are ligands for CCR4. In turn, secretion of these ligands attracts regulatory T-cells and malignant T-cells to the sites of the tumor, which results in a suppression of effector T-cells in the cancer cell environment. This suppression of the effector T-cells results in a favourable environment for continued cancer cell growth.
Previous work indicated that the use of a humanized anti-CCR4 monoclonal antibody, mAb2-3 IgG1, reduced the migration of regulatory T cells toward the CCR4 ligands, and ultimately resulted in a decrease of tumor size in in vivo tumor models. Regulation of both the migratory ability of regulatory and malignant T-cells toward the tumor cells, as well as direct cellular toxicity of the malignant cells, plays a key role in the progression of the cancer.